In the metal smelting and refining industries, reactants often need to be efficiently added to melts to maximize the yield of reaction products and to minimize the required time for processing. Reactants can be injected into the melt, for example, through tuyeres mounted in the molten bath reactor bottom or sides, or through submerged lances. In order to increase the efficiency of reactions within a molten bath or to augment the quality of the melt, attempts have been made to increase the rate of injection of reactants so that the greatest possible amount of molten metal is exposed to the added reactants at any given time.
Submerged injection at the bottom of a molten metal bath within a reactor generally includes disadvantages, such as discontinuities in the flow pattern of injected gas, causing the melt in the reactor to impact on the reactor bottom during injection. This is often referred to as "back attack" and can cause significant erosion of the refractory lining. Injection at the walls of reactors does not in itself eliminate or significantly reduce this problem and can cause other problems, such as flow of reactants at reactor walls, thereby causing increased corrosion and erosion of refractory material lining the reactor.
Submerged injection, particularly injection from the reactor bottom, can also suffer from solidification of portions of the molten bath in the region of injection consequent to formation of a relatively stagnant region in the molten bath immediately adjacent to the injection point, and to a cooling effect of injection. This solidification process typically leads to the formation of semi-permeable solid structures, so-called "accretions", which can interfere with the injection of gases and reactants.
Furthermore, bottom injection can also suffer from insufficient interaction between reactants directed into the molten bath, and thus incomplete treatment, owing to limited residence time of the reactants in the melt. Bottom injection can also result in metal being projected out of the reaction zone to produce skulling which can solidify on the reactor walls, and thus become unavailable for the process. Even worse, skulling can block off gas passages, thereby disrupting the normal operation of the reactor.
Therefore, a need exists for a method for submerged injection of a feed into molten baths which overcomes or minimizes the above-mentioned problems.